This invention relates generally to aerial vehicles, and relates with particularity to subsonic and supersonic aircraft having an increased airworthiness at low-speed flight with the advantage of a better control for takeoff and landing operations, and having a reduced high-speed flight air resistance enabling a better utilization of propulsion energy. One of the major problems associated with the design of modern fast aircraft is to provide means ensuring satisfactory lift, stability, and control of aircraft, not only at high-speed flight, but also at low-speed flight. In this respect the lift increasing means have passed an encouraging progress, but new means for improving stability and control at low-speed flight have less often been proposed. Thus it is obvious that the present great flight speed differences between the cruising speeds and the landing speeds are at variance with the applied conventional stability and control means whose serviceableness is inadequate, and that time has come to introduce new stability and control means in order to meet the present low-speed flight requirements and to provide some safety reserves for future developments.
A method of improving the conventional stability and control means, as contemplated by the present invention, involves a lengthwise travelling tail unit with circular arc motions, which increases the airworthiness of aircraft during low-speed flight and particularly at zero altitude operations.
Accordingly, it is an object of the present invention to provide new and improved stability and control means for modern fast aircraft.
Another object of the present invention is to provide new and improved stability and control means with reduced air resistance to save propulsion energy.
Another object of the present invention is to provide a new and improved variable geometry tail unit with high reliability of operation.
Another object of the present invention is to provide a new lightweight variable geometry tail unit.
Another object of the present invention is to provide a new variable geometry tail unit for subsonic or transsonic aircraft.
Another object of the present invention is to provide a new and improved variable geometry tail unit for supersonic aircraft.
Another object of the present invention is to provide a new and improved variable geometry tail unit for aircraft with variable geometry wings.
According to the present invention, the foregoing objects are attained by providing in powered aircraft travelling tail units with circular arc motions. The travelling tail unit consists of a tail unit-chassis with a longitudinal and airflow suitable shape and of the tail surfaces, attached to said chassis, which parts form a common monocoque construction. The said tail unit is connected with the aft end of the aircraft fuselage by means of four swivel arms, which are assemblied into a front swivel arm-frame and a hind swivel arm-frame. Both swivel arm-frames have hinges on their corners connecting them on their lower corners with said aft end of the fuselage and on their upper corners with said tail unit-chassis. By swivelling motions of said arm-frames the tail unit is moved upwards and rearwards - increasing the effective tail unit lever - for low-speed flight, or is moved forwards and downwards for high-speed flight, in which forward position the tail unit-chassis is joined in an airflow suitable manner to said aft end of said fuselage.
Within a first embodiment of the travelling tail unit are included further features which place said tail unit in its forward high-speed flight position in a horizontal distance behind the trailing edge of the aircraft wing. From this forward position the said tail unit is moved rearwards for low-speed flight and vice versa. The travelling tail surfaces may have smaller dimensions than fixed tail surfaces of conventional aircraft because the increased effective tail unit-lever during low-speed flight provides for balancing of moments. This reduces the air resistance during high-speed flight and saves propulsion energy.
In a second embodiment of the travelling tail unit, substantially provided for supersonic aircraft, the horizontal tail in its forward high-speed flight position is placed in a plane lying above the planes of the wings, and is so much moved forwards that the leading edges of said horizontal tail are positioned in front of the trailing edges of said wings. This reduces the supersonic impact wave resistance of the aerodynamically cooperating wings and horizontal tail on the basis of the Area Rule, and saves propulsion energy.
According to the present invention and on the basis of the foregoing two embodiments, three principal aircraft designs are provided. A first subsonic or transsonic aircraft design having fixed wings, a fuselage with jet engines placed on its aft end, and a travelling tail unit consisting of a tail unit-chassis and two inclined tail surfaces in V-tail arrangement. The rearward and forward travelling motions of the tail unit are accomplished by two swivel arm-frames, which also connect the tail unit-chassis with the aft end of the fuselage. In the forward high-speed flight position the tail unit is placed in a horizontal distance behind the trailing edges of the wings, from which forward position the tail unit is moved rearwards for low-speed flight and vice versa. The tail unit-chassis is also used as an airflow suitable fairing for an additional startbooster jet engine, which during high-speed flight is stopped and covered by the tail unit-chassis, but which during low-speed flight is uncovered and put into operation, and which increases the takeoff thrust of the zoom away thrust of the aircraft.
A second supersonic aircraft design having fixed wings with jet engines placed on their bottom sides, a fuselage, and a travelling tail unit consisting of a tail unit-chassis, a vertical tail, and a horizontal tail. The rearward and forward travelling motions of the tail unit are accomplished by two swivel arm-frames, which also connect the tail unit-chassis with the aft end of the fuselage. In the forward high-speed flight position the tail unit is placed in a horizontal distance behind the trailing edges of the wings, from which forward position the tail unit is moved rearwards for low-speed flight and vice versa. The tail unit-chassis is also used as an airflow suitable fairing for an additional startbooster jet engine, which during high-speed flight is stopped and covered by the tail unit-chassis, but which during low-speed flight is uncovered and put into operation, and which increases the takeoff thrust or the zoom away thrust of the aircraft.
The provision of startbooster jet engines specially adapted to zero altitude conditions is favourable for each high-altitude aircraft. It gives a better combustion efficiency connected with fuel savings and cleaner exhaust emissions on the airfields, and increases the propulsion redundancy. This is particularly valid for supersonic aircraft, whose main jet engines can be of simpler design, what in turn balances the costs of the startbooster engine.
A third supersonic aircraft design having variable geometry wings or fixed wings, a fuselage with jet engines in its aft end, and a travelling tail unit consisting of a tail unit-chassis, a vertical tail, and a horizontal tail. The rearward and forward travelling motions of the tail unit are accomplished by two swivel arm-frames, which also connect the tail unit-chassis with the aft end of the fuselage. In the forward high-speed flight position the horizontal tail is placed in a plane lying above the planes of the wings, and the leading edges of the horizontal tail are positioned in front of the trailing edges of the rearwards swung variable geometry wings or in front of the trailing edges of the fixed wings.
The swinging wings are connected with the travelling tail unit by means of special rods, what reduces the common motion forces for both devices. That is because the motions of the wings and the tail unit are always differently directed, with the air stream and against the air stream, and by said connection the air resistance forces on both devices are acting against themselves.